Anyway, I personally hope both Yonko live for a further Rocks plot. There is a point where all 11 supernova should be present for the downfall of at least these 2 Yonko. Bege's group actually has further plot with BM (hence why his cover story is happening now with Lola) and the next arc or 2 should cover Bonney and Urouge.
To me, it would be a sick alliance if all of the Supernova and SHF gathered under Luffy to take on Rocks, with BB/Shanks being heavily influenced into the story a well. By this point, Marco could also recruit the former division commanders and allies with Izo, and Luffy gains the full support of the WB pirates. This could/would lead into the final war.
I just think its more interesting that BM falling here in a lame way.
We really have to see what Kaido even wants in the end.